1. Field of the Invention
The invention relates to a coolable housing jacket for an electric motor, which takes the form of a moulded part manufactured by casting. To receive a coaxial or concentric internal rotor/stator arrangement including windings and winding overhang, the housing jacket is formed with a through-passage which is symmetrical, concentric and/or coaxial with respect to a hypothetical motor axis of rotation. Cooling is realised by means of circulation of coolant through one or more cooling channels penetrating the housing jacket.
2. Description of the Related Art
For the prior art, we refer first to DE 199 49 140 A1, DE 199 39 760 A1, DE 199 39 013 A1, DE 196 48 134 A1, DE 196 24 519 A1, DE 42 43 716 A1, DE 39 41 474 A1 and U.S. Pat. No. 5,084,642 A.
A generic electric motor with liquid cooling is described in DE 100 45 424. A housing jacket is formed hollow and is divided into plural channels through which coolant flows. On both sides of the electric motor in the respectively associated end shield is a connecting channel for the supply of cooling liquid from the housing jacket into the end shield. The end shield inner cavities are thus fully filled with cooling liquid, so that the bearings and couplings for pumps to be driven are cooled and simultaneously lubricated. The end shields are manufactured separately from the housing jacket as individual castings. As cooling liquid, hydraulic oil or water are mentioned, from which any impurities are removed by filtering in order to prevent blockage of the channels in the electric motor. However, the problem of corrosion is not addressed, and this is serious in the case of an aluminium housing jacket cooled by water which may become contaminated with dirt and impurities. There is a risk that then the aluminium may oxidise and corrode very rapidly. This then leads to internal rusting of the cooling channels and rust particles can become detached and block the cooling channel system.
Although corrosion protection by cathophoresis dip-varnishing in connection with electric motors is described in DE 43 06 897 A1, it is hinted to subject the stator itself, without factual connection with motor cooling, to a cathophoresis varnishing process, in which a first base coat is applied. Then, compulsorily according to the specification, a second subsequent dipping process is necessary, by means of which a low-viscosity single- or multiple-component varnish resistant to chemical influences is applied as a sealing coat. This is meant to achieve sealing of any pores and gaps remaining by the sealing coat, e.g. those that arise predominantly in corner regions or in the region of the starting copper after the application of the base coat, and hence the oxidation-resistance should be increased and corrosion of the stator and rotor materials excluded. Thus corrosion protection should be achieved for electric motors running in water, which act as a drive element for pumps, in particular split-pole motors.
The object of the invention is to increase the service life and reliability of the coolant flow circuit and of the whole cooling system of an electric motor with a coolable housing jacket of the type mentioned in the introduction. To achieve this, the coolable housing jacket indicated in claim 1 is proposed. Further details and advantageous embodiments of the invention will appear from the dependent claims.